protein need

First of all, thank you all for being here and being supportive. You all have been a great help as I still learn the ropes.

My question now is how much protein should I consume? I read Mark's guide that stated .5 g per lb of lean body weight, and up to 1 g for the active.

I have also read advocates of gauging protein on percentage of calorie intake, i.e., 15% of total calorie intake.

My problem is that I am drastically underweight and so am consuming an inordinate amount of calories for my body weight. If I eat protein according to Mark, I would require 39 g of protein at .5 or 77 at 1 g (yes, I am dangerously underweight). However, if I judge it by the percentage of caloric intake at 15% total, I should get 86 grams--a lot more than the 39 or 77.

I have heard that protein is the building block of the body, and I am trying to put on weight. But I have heard it is DANGEROUS to consume too much protein as well--it begins leaching from bones as too much is passed and I can't remember all.

In short, how much protein is good? Is it better to base on body weight or on caloric intake? How much is dangerous? What is healthy to put on weight?

Related, but not quite, is if I do reduce protein from 86 down to somewhere b/w 39 and 77, is it better to replace that with carbs or fat? (I get about 170 g. carbs right now, and the rest--about 50% of caloric intake--from fats).

also.... in total protein count, would you count grams of protein found in other foods than meat? i.e., a cup of brussel sprouts has 1 g. of protein, a potato (yes, I do eat safe starches) has 2 g. protein, etc. Do those count?

Thank you... I should 'worry" less, but my body is shutting down and health is in such precarious balance, adn doctors haven't been much help. So I worry more than I should. And it is more complicated b/c I am so underweight but consuming so much calories, the recommended can be different for that situation.

Allenete, you ask what typical food day is for me--I try for around 50-60% fat, 30% carbs from veggies and safe starches, and 15% protein.

Right now I am eating 2,500 calories a day. Despite taking betaine HCL and enzymes, i have trouble digesting food; the doctors just say "unknown malabsorption." I am seeing a new doctor next week, one who I found on the paleo physicians network and praying she can help-- my body is at such a low weight and has been for so long I am afraid it is starting to shut down, i.e., not producing the stomach acid and enzymes it needs, which just deprives it further nad leaches from the muscles and bones....

yup--colonoscopies, celiac sprue, endocsopies, barium tests, swallowing tests, stomach mobility tests, parasite tests, etc... more tests than i care to have had!!!! I do eat grain free and gluten free b/c i feel better--i do notice less bloating if i do NOT eat gluten or corn, etc.

but it is b/c of the drastic difference b/w my weight and my caloric intake that i am concerned about protein intake.